This invention relates to a method and apparatus for fuel control and, more particularly, to a method of and apparatus for fuel control capable of controlling a fuel injector so that an amount of fuel supplied into respective engine cylinders will be optimum.
In many fuel injection systems for automobile engines, an air passage from an air cleaner to respective engine cylinders is provided with a plurality of bore parts, for example, one bore part on the immediately downstream side of the air cleaner, and number of bore parts corresponding to the number of the engine cylinders on the manifold of the engine. A fuel injection system in which only one fuel injector is provided in a one bore part is, in the following description, designated as a one-bore one-injector system.
In, for example, Japanese Utility Model Laid Open Application No. 91474/1984, a one-bore one-injector system is proposed; however, when the system is applied to a multi-cylinder engine, the amount of fuel sucked or drawn into the respective cylinders scatter so that the operational control of the engine is insufficient.
Under the circumstances, a one-bore two-injector system in which two fuel injectors are provided in one bore part has been employed so that the fuel is supplied uniformly to respective cylinders. When a conventional one-bore two-injector system is applied to, for example, a four-cylinder engine, fuel is sucked four times and gaseous mixture is exploded four times per cycle (crank angle of 720.degree.). While these four suction strokes and four explosion strokes are made, the fuel is ejected twice from one injector, and twice from the other injector. The fuel is ejected from these two injectors alternately at an equal rate. The two injectors are arranged on the upstream side of a throttle valve and on a plane crossing a shaft of the throttle valve due to the construction of the engine. Under such arrangement of the two injectors, when the degree of opening of the throttle valve is at a certain level, the fuel ejected from one injector is sucked 100% but the fuel injected from the other injector is sucked only 80%, so that the quantity of fuel in the respective cylindrs becomes unbalanced. Therefore, when a conventional one-bore two-injector system is employed, sufficient engine torque does not occur, and the exhaust characteristics become inferior with the gaseous mixture not being completely combusted.
As mentioned above, in the conventional fuel injection systems, an amount of fuel supplied to the respective engine cylinders is not uniformly set.